The Environment – Ecosystem & Its Component SS1 Geography Lesson Note

Environment is defined as the total surrounding or medium of any organism in a given area. This includes the physical surroundings, climatic factors and other living organisms in that surrounding.

SPHERES OF THE ENVIRONMENT

The Earth as an environment is grouped into four spheres:

1. Lithosphere: The solid portion of the environment which contains rocks, sand, soil, minerals etc.
2. Hydrosphere: This is the liquid portion of the environment like rivers, lakes and oceans.
3. Atmosphere: This is the gaseous portion of the environment where gasses like oxygen, nitrogen, carbon dioxide, and ozone are found.
4. Biosphere: This is the portion of the environment where plants and animals are found.  

These four spheres of the environment are interrelated and interdependent.

ECOSYSTEM

Ecosystem: An ecosystem is defined as a community of plants and animals living together in harmony and interacting with their physical environment.

In other words, an ecosystem can be defined as the relationship that exists between living things and their nonliving environment.

Components of The Ecosystem

The ecosystem is made up of two main components.  These are:

1. Abiotic (non-living) components: These are the components like soil, water, gasses, sunlight etc in the environment.
2. Biotic component: This is the living component of the ecosystem.  It includes plants and animals.

Biotic components can be grouped into three:

i. Autotrophs: These are also called the producers.  They include the green plants which manufacture their food through a process known as photosynthesis.

ii. Heterotrophs: These are called primary and secondary consumers.  These organisms cannot manufacture their food but depend directly or indirectly on plants for their food e.g. man, parasites, saprophytes.

iii. Decomposers: These are microorganisms that decompose dead organic matter to release nutrients required by producers to prepare their food e.g. Fungi and bacteria. 

INTERDEPENDENCE WITHIN THE ECOSYSTEM

Interdependence is used to describe the relationship between the components of the ecosystem. This is because components in an ecosystem depend on one another and they cannot exist in isolation. A state of interdependence within the ecosystem is best achieved where the components are undisturbed.

Interdependence in an ecosystem exists in three ways:

1. Interdependence within Abiotic components e.g. The weathering of rock to form soil or the evaporation of water to form clouds etc.
2. Interdependence within Biotic components e.g. Animals depend on plants for food or the exchange of oxygen and carbon dioxides by plants and animals.
3. Interdependence between the biotic and abiotic components e.g. plants depend on soil for support and nutrients, Autotrophs convert sunlight to energy, water and carbon dioxide during photosynthesis to produce food etc.

ENVIRONMENTAL BALANCE

Environmental balance refers to the ways of recycling matter and the flow of energy within an ecosystem to ensure continuous supply or availability of energy.

Environmental balance is achieved through the following processes:

1. Hydrological (water) Cycle
2. Carbon Cycle
3. Nitrogen Cycle
4. Mineral or Nutrient Cycle
5. Food Chain and Food Web. 

ASSIGNMENT

1. The liquid portion of the earth is called ________(a) Hydrosphere (b) Biosphere(c) Atmosphere
2. Animals, man and parasites are grouped as ______(a) Decomposers (b) Heterotrophs (c) Autotrophs
3. The relationship between organisms and their physical environment is called __________(a) Environment     (b) Ecosystem     (c) Community
4. The best example of autotrophs are ______(a) Animals         (b) Man       (c) plants
5. One of these is not a way an environmental balance is achieved(a) Food chain   (b) Water cycle(c) Sand cycle
6. What is an ecosystem?
7. Mention four importance of the environment